The present invention relates to airbag apparatuses suitably installed in high speed vehicles such as automobiles, and particularly, it relates to airbag apparatuses in which an airbag is inflated with gas generated by a gas generator. More specifically, it relates to an airbag apparatus in which an amount of the gas introduced into the airbag from the gas generator is adjustable.
In some airbag apparatuses for protecting a passenger in a vehicle by inflating an airbag with gas generated by a gas generator, an amount of the gas introduced into the airbag is adjusted in accordance with a level of crash severity.
A dual-stage inflator is an example of such airbag apparatuses. The dual-stage inflator is provided with two combustion chambers, each filled with a gas generating agent, in its main body and is configured such that an amount of the gas introduced into an airbag is adjusted by separately igniting the gas generating agents in these two combustion chambers at different times.
In the airbag apparatus having the above-described dual-stage inflator, the inflator itself has a complicated structure, resulting in problems such as a high cost and an increased weight.
Another type of such airbag apparatuses is disclosed in U.S. Pat. No. 6,158,770 (incorporated by reference herein), comprising at least one gas vent opening disposed on a casing, a closing member covering the gas vent opening, and a shifter for opening the vent opening by shifting the closing member.
In the airbag apparatus disclosed in the foregoing U.S. Pat. No. 6,158,770, even when the vent opening is closed by the closing member, the gas generated by the gas generator is liable to leak through the vent opening.
Accordingly, an object of the present invention is to provide an airbag apparatus, in which an amount of the gas introduced into the airbag can be varied by shifting a closing member so as to open a vent opening. Another object is to minimize the amount of gas from leaking through the vent opening when the gas generator is activated while the closing member is in a closed state.
According to an embodiment of the present invention, an airbag apparatus includes a folded airbag; a casing to which the folded airbag is connected; a gas generator for generating gas for inflating the folded airbag; a plurality of vent openings disposed on the casing for discharging a part of the gas generated by the gas generator out of the casing; at least one closing member covering the vent openings; and at least one shifter for opening the vent openings by shifting the closing member. The closing member and the casing have a meltable layer interposed therebetween, the meltable layer being meltable by the gas generated by the gas generator, and the vent openings are covered by the meltable layer.
According to the embodiment described above, the closing member and the casing have the meltable layer disposed therebetween so as to cover the vent openings. The meltable layer serves as a gasket, thereby preventing the gas from leaking through the vent openings when the gas generator is activated while the closing member is in a closed state.
Preferably, the meltable layer serves as a part of the airbag, thereby eliminating any requirement for additional material for the meltable layer, thus, leading to a reduced production cost of the airbag apparatus.
According to the present invention, the closing member is preferably disposed in the casing. As a result, a pressure of the gas from the gas generator works to press the closing member against the casing, resulting in a simple mechanism for holding the closing member.
According to the present invention, the airbag apparatus is preferably configured such that the shifter is disposed outside the casing and the closing member has an outwardly extending portion which extends therefrom and which is connected to the shifter. This arrangement leads to a simple inside configuration of the casing, and also allows the shifter to be configured by selecting from a variety of mechanisms.
According to the present invention, a plurality of gas discharge ports of the gas generator are preferably disposed to face the corresponding vent openings so that the gas from the gas generator flows toward the vent openings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.